CVE-2024-50186

In the Linux kernel, the following vulnerability has been resolved:

net: explicitly clear the sk pointer, when pf->create fails

We have recently noticed the exact same KASAN splat as in commit 6cd4a78d962b ("net: do not leave a dangling sk pointer, when socket creation fails"). The problem is that commit did not fully address the problem, as some pf->create implementations do not use skcommonrelease in their error paths.

For example, we can use the same reproducer as in the above commit, but changing ping to arping. arping uses AFPACKET socket and if packetcreate fails, it will just sk_free the allocated sk object.

While we could chase all the pf->create implementations and make sure they NULL the freed sk object on error from the socket, we can't guarantee future protocols will not make the same mistake.

So it is easier to just explicitly NULL the sk pointer upon return from pf->create in _sockcreate. We do know that pf->create always releases the allocated sk object on error, so if the pointer is not NULL, it is definitely dangling.